Gamma glutamyl transferase

Serum gamma-glutamyl transferase (GGT) has been widely used as an index of liver dysfunction and marker of alcohol intake. The last few years have see n improvements in these areas and advances in understanding of its physiolo gical role in counteracting oxidative stress by breaking down extracellular glutathione and making its component amino acids available to the cells. C onditions that increase serum GGT, such as obstructive liver disease, high alcohol consumption, and use of enzyme-inducing drugs, lead to increased fr ee radical production and the threat of glutathione depletion. However, the products of the GGT reaction may themselves lead to increased free radical production, particularly in the presence of iron. There have also been important advances in the definition of the associatio ns between serum GGT and risk of coronary heart disease, Type 2 diabetes, a nd stroke. People with high serum GGT have higher mortality, partly because of the association between GGT and other risk factors and partly because G GT is an independent predictor of risk.